- Add gadget_cribjs_page_snapshots: snapshot list with compare/restore actions
- Add gadget_cribjs_page_compare: side-by-side diff viewer using diff_match_patch
- Add lib/diff_match_patch.js for text diffing
- Various UX updates: home, export, import, templates, tools, app lists, global gadget

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>